Structure of the Lithosphere and Upper Mantle in den Ocean-Continent Transition from SS Precursors

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We propose to use the large amount of seismic data recorded by the GRSN and Gräfenberg stations to study the lithosphere and mantle transition zone in the continent-ocean transition with SS precursors. SS bounce points from events in the seismically very active region of the southwest Pacific sample a corridor from the Aleutians, Kamchatka and the Japan subduction zone through the North China craton to the Tibetan plateau. The corridor passes different tectonic units such as subduction zones, an old continental shield, a fold belt and a high plateau. We will investigate the lithosphere and the mantle transition beneath different geologic units along the corridor and infer geodynamic processes at depth. We will search for higher resolution evidence for the earlier proposed structural differences between continents and oceans down to the mantle transition zone. High resolution images of SS precursors may also reveal the interaction of the subducted oceanic lithosphere with the mantle transition and serve to answer the often debated question about the scale and extent of the slab stagnation within the mantle transition zone beneath the NW Pacific subduction zone. We will attempt to use the short period content of SS waveform data and experiment with methods like CMP stack and migration techniques to acquire high resolution lithosphere and upper mantle images and to improve the lateral and depth resolution for the upper mantle discontinuities and, further more, to create new possibilities to study the shallower structures such as the lithosphere-asthenosphere boundary with SS precursors.